Don't take too much for your first time. No exceptions. You need to develop the familiarity with this state of consciousness. It's always possible to do stupid things while under the influence, especially for a first-timer on some heroic dose.
You don't have to be an expert at meditation, but it helps to be a little familiar with open awareness.
Make sure your environment is comfortable and has good vibes. If you have a sitter it should be someone you trust.
Have plenty of water and light snacks (fresh fruit is great) on standby.
For me, when the bulk of the trip is over but I'm still woozy, I have to force myself to get some fresh air to lift my mood. Some people need uplifting music or a funny video.
If you feel lethargic when you sober up, it's normal and temporary. You need to get rest, have a good meal, and digest your experience. Journaling is good.
And remember that any revelations you get have to be filtered through your unique brain and memories. The emotional content is where the core meaning is -- all the mental imagery and abstract concepts and such are valuable and beautiful but they are not literal. Like, people who do a drug and come out of it insisting that there is a specific species of alien doing a specific thing to humanity, or whatever, are missing the point of the experience.
Safe travels! I kind of wrote a lot, but really in the end all you have to do is relax.